A conventional dispensing device for supplying heated adhesive (i.e., a hot-melt adhesive dispensing device) generally includes an inlet for receiving adhesive materials in solid or liquid form, a heater grid in communication with the inlet for heating the adhesive materials, an outlet in communication with the heater grid for receiving the heated adhesive from the heated grid, and a pump in communication with the heater grid and the outlet for driving and controlling the dispensation of the heated adhesive through the outlet. One or more hoses may also be connected to the outlet to direct the dispensation of heated adhesive to adhesive dispensing guns or modules located downstream from the dispensing device. Furthermore, conventional dispensing devices generally include a controller (e.g., a processor and a memory) and input controls electrically connected to the controller to provide a user interface with the dispensing device. The controller is in communication with the pump, heater grid, and/or other components of the device, such that the controller controls the dispensation of the heated adhesive.
Conventional hot-melt adhesive dispensing devices typically operate at ranges of temperatures sufficient to melt the received adhesive and heat the adhesive to an elevated application temperature prior to dispensing the heated adhesive. In order to ensure that the demand for heated adhesive from the downstream gun(s) and module(s) is satisfied, the adhesive dispensing devices are designed with the capability to generate a predetermined maximum flow of molten adhesive. As throughput requirements increase (e.g., up to 20 lb/hour or more), adhesive dispensing devices traditionally have increased the size of the heater grid and the size of the hopper and reservoir associated with the heater grid in order to ensure that the maximum flow of molten adhesive can be supplied.
However, large hoppers and reservoirs result in a large amount of hot-melt adhesive being held at the elevated application temperature within the adhesive dispensing device. This holding of the hot-melt adhesive at the elevated application temperature may keep the hot-melt adhesive at high temperature for only about 1 to 2 hours during maximum flow, but most conventional adhesive dispensing devices do not operate continuously at the maximum flow. To this end, all adhesive dispensing devices operate with long periods of time where the production line is not in use and the demand for molten adhesive is zero, or lower than the maximum flow. During these periods of operation, large amounts of hot-melt adhesive may be held at the elevated application temperature for long periods of time, which can lead to degradation and/or charring of the adhesive, negative effects on the bonding characteristics of the adhesive, clogging of the adhesive dispensing device, and/or additional system downtime.
In addition, the supply of adhesive material into the hopper must also be monitored to maintain a generally consistent level of hot-melt adhesive in the adhesive dispensing device. Adhesive, generally in the form of small shaped pellets, is delivered to the hopper with pressurized air that flows through an inlet hose at a high velocity (the pellets move at about 70% of the speed of the air). In conventional adhesive dispensing devices in which the inlet hose is directly connected to the hopper, the high rate of pellet and air speed may cause splashing of molten adhesive that can build up and lead to blockages of either the inlet or the air exhaust at the hopper. The inlet and the air exhaust may include baffles to limit such splashing of molten material, but these baffles provide an additional surface area that molten material can build up on and cause blockages.
In other conventional adhesive dispensing devices, a tapered cyclonic separator unit may be located between an inlet hose and a hopper. The tapered cyclonic separator unit effectively slows or stops the flow of the air and allows the material moving within the air to be dropped by gravity into the hopper. When used with adhesive pellets, the tapered walls of the cyclonic separator unit slow down the flow of adhesive pellets by frictional engagement, but the high amount of frictional engagement with the adhesive pellets caused by the significant taper or angle of the walls may cause adhesive build up on the walls and the eventual clogging of the inlet at the end of the cyclonic separator unit.
For reasons such as these, an improved hot-melt adhesive dispenser device and cyclonic separator unit would be desirable.